"Fat Boy" 12/118 thrust engine

[racket]

LOL..........nice strong buffalo turf, only needs mowing every second week even during a hot wet summer ;-)

[smithy1]

LOL...I have Buffalo in my back yard too...Matilda Buffalo...it's nice and dense and like yours, it only needs mowing every other weekend..!

Smithy.

[racket]

Hi Smithy

LOL.........the cheap arse developer who built five $600K houses down the road only laid Kikuyu and its growing up the fences in two weeks , bastard , the new owners are mowing every few days :-(

Cheers
John

[smithy1]

Bugger that....I'm too lazy to cut the grass every couple of days....heck...I don't even like doing it every couple of weeks..!

On a side note....Smithy now has a "propane free" fuel only start engine..! Still have a couple of bugs to iron out but it works..!  

Smithy.

[racket]

Hi Guys

IGV welded together,installed into bellmouth using silicone bead on each side of the vanes , port cut into hub for the starter coupling tach reading









Tomorrow I'll do some starter rpm testing to see if theres been any changes , hopefully a few more rpm from the unloading of the comp wheel.

Cheers
John

[smithy1]

Very Noice Sir...!!

[Johansson]

It looks really good John, hope you see more RPM on the starter now.

[smithy1]

Would a higher voltage through the starter be of any help John??....Might get you over the "hump"...

Smithy.

[racket]

Hi Smithy

Yep , I've considered adding another 12 volts , 36 volts thru the starter would be interesting, I've also considered impingement from very high pressure gas to help the current 24 volts , maybe just a few seconds squirt from the oxy bottle once the starter starts to struggle .

The next test run will be with the "old" jetpipe just to find out any differences the IGV makes .

Off to the shed to try some dry testing ;-)

Cheers
John

[racket]

Hi Guys

Just completed a few "dry" starter runs ..............looking promising :-)

Before the test the 2 X 12V batteries each had ~12.8 V in each , they were recharged over a week ago so not freshly charged, which would probably add another 0.5V .

Oil pressure 73 psi at 25 deg C

The first test resulted in 12,600 rpm, this is ~1,000 rpm more than last test on 15th Nov .

Now horsepower required sorta goes up as the square of the tip speed , at 12,600 rpm the tip speed of comp is ~340 ft/sec - 230 mph , at the old 11,600 rpm only ~312 ft/sec , when we square those numbers the 12,600 rpm "theoretically ?? " requires ~19% more energy , or in my case I've "deffered" that 19% because of the prewhirl .

After 3 tests the rpm were down to the old 11,600 rpm , but the starter motor was too hot to hold onto and batteries were down to ~12.5 V each. I'm recharging them and will do another set of runs with freshly charged batteries.

LOL............there seems to be a "positive" improvement :-)

Cheers
John

[jetjeff]

Good to hear, John.

Regards

Jeff

[turboron]

John, one observation related to your with pre-swirl change is that most gas turbines with axial compressors now have variable Inlet Guide Vanes (IGVs) for the first few rows of vanes. They are partly closed during starting which reduces the mass flow. In addition, most axial compressors have interstage bleed valves to match the flow to the area reduction while starting. The IGVs are opened and the bleed values are closed at idle. Perhaps a bleed downstream of the compressor along with the squirt of gas will be the solution.

Thanks, Ron

[smithy1]

Hmmm....I would've thought anything over 10,000rpm dry would be enough to see you over the hump, taking "post ignition" fuel help into account...When we ran your engine at the go kart track some time back, she started really easily and ran beautifully...An engine that size should be able to self sustain ~20k rpm....even the 6041 will happily spin over at ~18k, any lower and she starts getting a bit warm.

What viscosity oil are you running John..?? Might also pay to drop the oil pressure a tad during start to help it along a bit. Just run a little bypass valve back to tank in the pressure line and open it up a bit during start, then when you have a stable idle, close it off..!

Which reminds me...I'll be up at Newcastle Go Kart track, Cameron Park on Sunday 10th December for a car show...if you're up to traveling, come down, would love to catch up again.

Smithy.

[racket]

Hi Smithy

With batteries charged , 13.5 and 13.6 V she spun to 12,800 rpm , only another couple of hundred rpm but probably worth making sure they're fully charged next test run .

To see what the oil pressure is doing , I conducted a run without the oilpump operating , 13,700 rpm was the result , not a massive difference but certainly a decent chunk of starter power , ~15% , required to overcome the extra friction from 70 psi of oil pressure.

If only she'd be as mild mannered as the 6041 , she's a draught horse whilst the 12/118 is a skittish racehorse .............I need at least 30,000 "wet" on the starter to have any chance of a successful spoolup, and then its gotta idle at more than 0.5 Bar P2 at 32,000 with the "old " jetpipe ............with the new pipe its gunna be even worse I feel ............LOL, its probably gunna end up like a 1960s two stroke racebike , nothing below 90% rpm then a wild burst of power :-)

Newcastle visit would be nice , but too much happening on the runup to Christmas and I'm pacing my energy output especially now that summer has finally arrived , hot and sticky isn't go well with my health :-(

Cheers
John

[racket]

Hi Ron

Hopefully the IGV combined with the bleed slot will "calm" down the engine enough , thankfully I've plenty of rpm reserves to restore P2 and flow once up at max .

Impingement is certainly the easiest to fit and operate , get her up to "hung start" on the starter then hit the impingement for a couple of seconds to get those crucial extra rpm .

Cheers
John